The invention relates to an arrangement for measuring the gap between two rolls or rollers, comprising a measuring body on which at least three support rollers that get into contact with a surface of one of the rolls or rollers are provided on one side to adjust the measuring body between the rolls or rollers, two of which support rollers are located on either side of the gap to be measured, being symmetrical with respect to the gap plane, and at least two support rollers that get into contact with the surface of the second roll or roller at contact points located symmetrical to the gap plane, are provided on the opposite side of the measuring body. At least two support rollers for the one roll or roller, that are arranged symmetrical to the gap plane, are synchronously movable towards the surface of the roll or roller and are pressable at the same. The measuring body is provided with two diametrically opposite measuring tracers, whose measuring heads are movable in a symmetrical plane between the support rollers that get into contact with the surfaces of the rolls or rollers on either side of the gap plane, i.e., are movable in the gap plane towards the surfaces of the rolls or rollers. The invention also relates to a method for carrying out the measurement.
In a know measuring arrangement (German Offenlegungsschrift No. 1,752,947), the axes of the support rollers are arranged parallel to the axes of the rolls forming the gap to be measured. The rollers retainers and are pressable at the surfaces of the rolls to be measured. The distance between the roller retainers arranged on either side of the gap plane distorting to determine the gap width between the rolls, which distance is applied to calculate the width of the gap to be measured provided the roll diameter is known.
With this known measuring arrangement it is, thus, not the gap proper that is measured, but the distance between the roller retainers. A disadvantage of this method is that the measured result must be calculated by taking into account the geometric features of the measuring arrangement and of the rolls, with allowances being made for the parts of the measuring device and of the rolls. With large roll diameters, a strong wedge action occurs at the roller retainers, the measured result thus being influenced by the force adjusting the roller retainers to the roll surfaces.
A further disadvantage of this known device is that roll generatrices lying outside of the gap plane are measured, whereby deviations of the roll shapes from the ideal geometric shape enter into the measured result, distorting the latter.
A measuring arrangement of the initially defined kind is known from German Auslegeschrift No. 2,639,240. With this measuring arrangement, the gap between two rolls or rollers is measured precisely in the gap plane, i.e., in the plane through the axes of the oppositely arranged rolls or rollers; yet, the support rollers are motionally coupled with the measuring heads, the measured result thus being influenced by the pressure forces of the support rollers exerted on the rolls or forming the gap to be measured.
A further so not have the necessary accuracy. measuring arrangement is in that the measuring procedure is feasible always at one single point only of the longitudinal extension of the roll or roller to be measured. In order to be able to exactly measure the gap over its total length, the known measuring arrangement must be removed from the gap, be displaced in the axial direction of the roll or roller and be reinserted into the gap. This is cumbersome and time-consuming and, if the rolls or rollers of two consecutive measurements are not precisely fixed in their positions, this may lead to inexact results, particularly if the rolls or rollers have a cross section deviating from the circular shape.
Furthermore, it is known with cold or hot rolling stands for rolling metals, to detect changes of the rolling gap which occur due to mechanical wear, regrinding, thermal influences on the surfaces of the rolls and dead weight forces of the rolls, by means of complex mathematical models, and to carry out the appropriate correctional measures without performing any measurements. This suffers the disadvantage that the actual shape of the rolling gap is not seized at all. For an effective correction, the calculated values do not have the necessary accuracy.
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide an arrangement of the initially described kind as well as a method for exactly measuring the gap and determining the surface shape of the rolls or rollers in the gap plane, with sources of errors that distort the measured result being avoided. In particular, the gap is to be simply measured over its total length and the measured result is to remain unaffected by the forces pressing the support rollers at the surfaces of the rolls or rollers.